Process of dyeing acrylonitrile articles with cationic dyes



the rule.

PROCESS OF DYEING ACRYLONITRILE ARTICLES WITH CATIONIC DYES Leonard S. Pitts, Waynesboro, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Mar. 28, 1957, Ser. No. 649,010

14 Claims. (Cl. 855)' This invention relates to uniform dyeing of acrylonitrile polymeric structures with cationic or basic dyes. More specifically, the invention is directed to level dyeing in pastel shades of fibers, filaments, yarns, fabrics, and the like of acrylonitrile polymers with basic dyes.

When acrylonitrile polymeric fibers, fabrics and the like are dyed to light shades with cationic (basic) dyes (0.01% to 0.2% dye in fiber), unlevel dye application is The less the amount of dye applied, the serious the non-uniformity problem. This problem of non-uniformity is largely a function of the comparative rates at which the dye is removed from the bath and the time that'the fabric requires to reach equilibrium temperature and saturation with respect to the dye bath. For best results, the dyeing rate should be slow compared to the rate at which the fabric wets out. In practical dye house work, if the exhaust times for removing dye from the bath are in excess of 30 minutes, good levelnesscan be attained without the need of special agents to slow down the dyeing rate. In pastel shades, however (0.01%0.2% dye in fiber), exhaust times range from one minute to 15 minutes, and unlevel application results because the portions of the fabric which wet out more rapidly exhaust the limited supply of dye from the bath, leaving little or none for the less rapidly dyeing portions. This phenomenon is termed in the trade strike-on. With other classes of dyes and fibers, for example, dispersed dyes on acrylonitrile polymeric fibers and selected anionic (acid) dyes on wool, either strike-n does not occur or if it does occur, the dye can be leveled by an additional boil which causes the dye to distribute itself evenly over the fabric. With cationic dyes on acrylonitrile polymeric fibers, this leveling operation does not work because this class of dye does not migrate from dyed fiber to undyed fiber with any ease. The problem of strike-0n must therefore be avoided during the application of dye if levelness is to be obtained.

In. current application of cationic dyes at low concentration, cationic retarders (alkyl quaternary nitrogen compounds) are used with good results. Presumably these materials compete with the dye for dye sites, thus slowing down the dyeing rate so that exhaust times are increased to over 30 minutes. With these retarders Wetting or leveling agents such as a polyethylene oxide and Glaubers salt are used. A typical dyeing formulation for level dyeing to pastel shade is given below:

0.1% cationic dye 0.5% leveling agent (such as a polyethylene oxide) 0.3% sodium acetate 0.4% glacial acetic acid 6% cationic retarder (quaternary nitrogen compound) Glaubers salt 40:1 dye bath The chief disadvantage in the use of the cationic retarder is that occasional non-level application, resulting from mistakes or mechanical breakdown, cannot be easily salvaged by overdyeing to deep colors. The cationic retarder being substantive on acrylonitrile polymeric fibers utilizes too many of.the dye sites, and the retarder must be stripped from the fabric in order to re-expose the dye sites, which stripping operation raises the dyeing costs very substantially. It cannot be used with wool blends because the wool is degraded by the stripping operation. A retarder which does not require stripping for the overdyeing operation would reduce dye costs for dyeing acrylonitrile polymeric fibers and provide a method whereby wool blends could be salvaged.

It is therefore an object of this invention to provide a method of uniformly dyeing in pastel shades acrylonitrile polymeric materials with a cationic or basic dye. Another object is the provision of a method of obtaining uniform dyeing of acrylonitrile polymeric materials in pas-tel shades by the exhaustion method.

Still another object is the provision of a dyeing method which is applicable to polyacrylonitrile and wool mixtures. Other objects will appear as the description of the invention proceeds.

These and other objects are accomplished by the use of retarders capable of giving level dye application and which are not substantive to acrylonitrile polymeric fibers such as polymeric sulfonic acids in the range of molecular weights from about 6,000 to about 100,000 and preferably from about 10,000 to about 70,000. The most practical example of this type of retarder is the water-soluble salts of after-sulfonated polystyrene. Polymers and copolymers of monomeric sulfonic acids may also be used. However, the effectiveness is dependent on the number of sulfonate groups in the polymer. The polymeric sulfonates must be water-soluble or water dispersible. Sodium polystyrenesulfonate prepared from polystyrene by after-sulfonation having a molecular Weight of 70,000 and sodium polystyrene-sulfonate prepared from polystyrene by after-sulfonation having a molecular weight of 10,000 were both found to be very effective.

As might at first appear to be the case, the polymeric sulfonate does not tie up the dye irreversibly, and therefore does not consume large quantities of dye. The reaction between the polymeric sulfonate and the dye molecule is reversible compared to reaction between dye and fiber and in the case of most dyes tested all except traces of the dye can be exhausted into the fiber. As the dyeing proceeds, dye removal from the polymeric sulfonic acid in solution becomes more and more difiicu-lt. However, the small amount of dye left at the end of a normal dyeing cycle is not of economic importance.

As earlier stated, any water-soluble or colloidally dispersed polymeric sulfonic acid or ionizable salt thereof having a molecular weight of at least about 6,000 and preferably at least about 10,000 is useable in accordance with this invention. In addition to after-sulfonated polystyrene, other polymeric materials capable of being aftersulfonated may also be used or polymers and copolymers may be prepared from monomeric sulfonics' such as styrenesulfonic acid, styrenedisulfonic acid, vinylsulfonic acid, methallylsulfonic acid, methacryltauride, etc. The concentration of the polymeric sulfonic acid in the dye bath may vary very widely depending on the depth of color to 'be imparted to the acrylonitrile polymeric goods and the tinctorial power of the dyes used. Weight concentrations in the range from 0.1% to 10% based on the weight of the fabric to be dyed may be used but, generally, concentrations of from 0.5% to 6% will be found most useful for the average dye house.

In addition to the polymeric sulfonic acids, polymeric compounds containing free carboxylic acids or phosphonic acids or their ionizable salts may also be used to advantage with varying degrees of success but these are less efiicient than polymers of the sulfonic acids. A few such compounds are polymers of acrylic acid, methacrylic acid,

itaconic acid, propene-Z-phosphonic acid, styryl phosphonic acid, etc.

The invention is applicable to any acrylonitrile polymer or copolymer structure having at least 85% acrylonitrile content containing some acidic groups as basic dye sites. It is especially applicable to those copolymers containing from about 0.1% to of copolymerized ionizable sulfonate monomer and up to about of an ethylenically unsaturated monomer copolymerizable therewith.

Examples to illustrate dyeing without a retarder, with a retarder of the prior art and with the retarders of this invention are given below. Parts are by weight unless otherwise specified.

EXAMPLE 1 A dye bath was prepared using 0.02% of a violet cationic dye of' Color Index 681 (Crystal Violet) on the weight of the fabric to be dyed in sufficient water togive a 40:1 dye bath on fabric weight. An acrylonitrile copolymer of about 94% acrylonitrile, 5.7% methyl acrylate and 0.3% sodium styrenesulfonate in the form of a spun yarn fabric sample was introduced into the boiling dye bath. Complete exhaustion of the dye bath occurred in one minute. The fabric was unevenly dyed, showing many portions of heavy dyeing with little or no dyeing in other portions. I

EXAMPLE 2 A dye bath was prepared using the same recipe as Example 1 except the addition of 2.5% to 3% of a quaternary nitrogen. cationic retarder. A sample of the same fabric as in Example 1 was introduced into the boiling dye bath. The bath was exhausted in minutes. The sample was evenly dyed with no visual evidence of nonuniformities. ter a 15-minute scour in boiling water, the sample was introduced into a bath containing a formulation of cationic dyes suflicient to dye the fabric of Example 1 to a deep black within two hours. The sample in this case was only capable of dyeing to a gray black, however. In crderto reach a deep black, it was necessary to boil the fabric in 0.1% soap solution for one hour prior to the second dyeing.

EXAMPLE 3 A dye bath was prepared using the same recipe as Example 1 except for the addition of 1%, based on the fabric, of sodium polystyrenesulfonate in the bath. The fabric like that of Example 1 was introduced into the boiling dye bath and the bath was exhausted except for a slight trace of dye within minutes. proved to be dyed as evenly as the fabric of Example 2. It was possible to overdye this fabric, unlike the fabric of Example 2, to a jet black without any additional treatment.

EXAMPLE 4 Dye baths were prepared using 0.2% of each of the dyes listed below and 1% of sodium polystyrenesulfonate based on the weight of fabric to be dyed. A 40:1 dye bath was used. Fabric samples like that of Example 1 were dyed to even shades in this bath with an exhaust time of about minutes. All the fabrics were capable of overdyeing to jet black without further treatment.

Table Yellow cationic dye of Color Index 655 (Auramine) Yellow cationic dye of Color Index 815 (Thiofiavine T) Orange cationic dye of Color Index 21 (Chrysoidine) Red cationic dye of Color Index 677 (Fuchsine) Red cationic dye of Color Index 841 (Safranine T) Blue cationic dye of Color Index 729 (Victoria Blue) Blue cationic dye of Color Index 922 (Methylene Blue) Blue cationic dye of Color Index 663 (Lithosol Blue G) Blue cationic dye of Color Index 658 (Lithosol Blue 6G) Green cationic dye of Color Index 662 (Brilliant Green) Green cationic dye of Color Index 657 (Malachite Green) Violet cationic dye of Color Index 749 (Rhodamine B) Violet cationic dye of Color Index 681 (Crystal Violet) The fabric 4 EXAMPLE 5 A dye bath was prepared using 0.1% of a violet cationic dye of Color Index 681 (Crystal Violet) and 3% of sodium polystyrenesulfonate based on the weight of the fabric to be dyed. A 40: 1 dye bath was used. The fabric to be dyed was composed of'yarns of an acrylonitrile copolymer of about 98% acrylonitrile and 2% sodium styrenesulfonate (containing approximately six times as many dye sites as the samples of the previous examples). The fabric was dyed to an even pastel shade in this bath with an exhaust timeof about minutes. The. fabric was capable of overdyeing to jet black without further treatment. W

EXAMPLE 6 A 70/30 wool-acrylonitrile polymeric fiber (of the composition of Example 1) blend was dyed in the following bath:

EXAMPLE 7 A dye bath was prepared using the same recipe as Example 1 except for the addition of 1% based on the fab ric of sodium polystyrenesulfonatein the bath. An acrylonitrile polymer of about 94% acrylonitrile, 5% methylacrylate and 1% acrylic acid in the form of a spun yarn fabric was introduced into the bath and the bath was exhausted except for a trace of dye within 40 minutes. The fabric proved to be dyed as evenly as the fabric of Example 2, whereas the same fabric in the absence of the sodium styrenesulfonic acid dyed unevenly as in the case of the fabric of Example 1.

EXAMPLE 8 Into the dye bath prepared as in Example 7, a spun yarn fabric of acrylonitrile copolymer fibers consisting of about 94% acrylonitrile, 4.5% methyl acrylate, and 1.5% styryl-2-phosphonic acid is introduced and the bath is exhausted except for a trace of dye within 45 minutes.

The fabric isdyed evenly, whereas, in the absence of the polymericsulfonate, the same fabric is dyed unevenly as in the case of Example 1.

The invention is of greatest value in light shade dyeing of acrylonitrile polymeric structures containing ample sulphonic acid dye sites for jet black dyeing with cationic dyes. However, through the use of this invention, levelness of pastel shade dyeing will be found possible with acrylonitrile polymers containing only the minimum of sulfonic and sulfuric groups resultin from polymerization of acrylonitrile with or without other comonomers in the presence of a persulfate catalyst and a bisulfite or similar activator. Other copolymers of acrylonitrile containing a small amount of carboxylic or phosphonic acid groups such as acrylic, methacrylic, itaconic, propene-2-phosphonic or styryl-2-pl1osphonic acids or ionizable salts thereof are also more uniformly dyed by means of this invention.

It will be apparent that many widely different embodiacrylonitrile copolymer having anionic groups as basic dye sites, which comprises dyeing the said material in a dye bath containing a cationic dye and an ionizable water miscible polymeric sulfonate having a molecular weight from about 6,000 to about 100,000 the said copolymer having a polyacrylonitrile content of at least 85%.

2. The process of claim 1 in which the ionizable polymeric sulfonate is a sulfonic acid.

3. The process of claim 1 in which the ionizable polymeric sulfonate is in the form of a water-soluble salt.

4. The process of claim 1 in which the molecular Weight of the polymeric sulfonate is from 10,000 to 70,000.

5. The process of claim 1 in which the concentration of the said polymeric sulfonate is from 0.1% to based on the weight of the material to be dyed.

6. The process of claim 1 in which the concentration of the said polymeric sulfonate is from 0.5% to 6% based on the weight of the material to be dyed.

7. The process of claim 1 in which the material is a fabric.

8. The process of claim 1 in which the material to b dyed is a filament.

9. The process of claim 1 in which the acrylonitrile polymer is a copolymer containing from 0.1% to 5% of an ethylenically unsaturated monomer having ionizable acid groups copolymerizable with acrylonitrile.

10. The process of claim 1 in which the acrylonitrile polymer is a copolymer containing from 0.1% to 5% of an ethylenically unsaturated monomer having ionizable sulfonate groups copolymerizable with acrylonitrile.

11. The process of claim 1 in which the acrylonitrile polymer is a copolymer containing from 0.1% to 5% of an ethylenically unsaturated monomer having ionizable carboxylic groups copolymerizable with acrylonitrile.

12. The process of claim 1 in which the acrylonitrile polymer is a copolymer containing from 0.1% to 5% of an ethylenically unsaturated monomer having ionizable phosphonic groups copolymerizable with acrylonitrile.

13. The process of claim 9 in which the acrylonitrile polymer contains in addition thereto up to about 15% of a non-ionic ethylenically unsaturated monomer copolymerizable with acrylonitrile.

14. The process of claim 1 in which the polymeric material contains about 94% acrylonitrile, about 5.7% methyl acrylate, and about 0.3% sodium styrene sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 2,604,456 Signer July 22, 1952 2,612,485 Baer Sept. 30, 1952 2,669,557 Wheaton Feb. 16, 1954 2,718,514 Fantl Sept. 20, 1955 2,726,132 Craig Dec. 6, 1955 OTHER REFERENCES Clarke: Amer. Dyestufi Rep., August 29, 1955, p. 534. Speel: Textile Chemicals and Auxiliaries, 2nd ed., 1957, Reinhold Pub. Co., N.Y., p. 337.

, UN'ELTE STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2,955,009 October 4 1960 Leonard S, Pitts It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 line 23, before "serious" insert more Signed and sealed this 23rd day of May 1961.-

Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. THE PROCESS OF DYEING MATERIALS COMPRISING AN ACRYLONITRILE COPOLYMER HAVING ANIONIC GROUPS AS BASIC DYE SITES, WHICH COMPRISES DYEING THE SAID MATERIAL IN A DYE BATH CONTAINING A CATIONIC DYE AND AN IONIZABLE WATER MISCIBLE POLYMERIC SULFONATE HAVING A MOLECULAR WEIGHT FROM ABOUT 6,000 TO ABOUT 100,000 THE SAID COPOLYMER HAVING A POLYACRYLONITRILE CONTENT OF AT LEAST 85%. 